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United States Patent |
6,228,439
|
Watanabe
,   et al.
|
May 8, 2001
|
Thin film deposition apparatus
Abstract
An apparatus for manufacturing information recording disks is disclosed.
The apparatus includes a deposition chamber for providing an undercoat
layer to a substrate to be treated, a deposition chamber for providing a
magnetic recording layer on the substrate, a deposition chamber for
providing a protective layer over the recording layer and a holding
chamber for removing the resulting information recording disk upon
completion of the process steps. The deposition chamber which provides the
protective layer includes a system which selectively introduces heated
plasma and oxygen into the interior of the deposition chamber to clean the
interior surfaces of the chamber while the apparatus is in use. The heated
plasma and oxygen interact with any excess protective layer material,
resulting in the formation of a gas which is removed from the interior of
the deposition chamber by a pumping system. The holding chamber is used to
remove and maintain the processed information recording disk while the
interior of the deposition chamber is being cleaned.
Inventors:
|
Watanabe; Naoki (Kodaira, JP);
Watabe; Osamu (Fuchu, JP);
Hayashida; Hideki (Tachikawa, JP)
|
Assignee:
|
Anelva Corporation (JP)
|
Appl. No.:
|
610721 |
Filed:
|
July 6, 2000 |
Foreign Application Priority Data
| Feb 16, 1998[JP] | 10-050191 |
Current U.S. Class: |
427/585; 118/719; 427/248.1; 427/569; 438/689; 438/706 |
Intern'l Class: |
C23C 016/00; C23C 008/00; H05H 001/00 |
Field of Search: |
118/719,695,715,723 R,718
156/345
427/569,585,248.1
438/706,689
|
References Cited
U.S. Patent Documents
4816113 | Mar., 1989 | Yamazaki | 156/643.
|
5505779 | Apr., 1996 | Mizuno et al. | 118/719.
|
Primary Examiner: Mills; Gregory
Assistant Examiner: Hassanzadeh; P.
Attorney, Agent or Firm: Coudert Brothers
Parent Case Text
This is a continuation of application Ser. No. 09/250,033, filed Feb. 12,
1999, which claims the benefit of U.S. Provisional Application Serial No.
60/076,618, filed Mar. 3, 1998.
Claims
What is claimed is:
1. A method for processing substrates comprising,
placing at least one substrate in a substrate processing system having a
plurality of processing chambers, at least two of said processing chambers
being deposition chambers each having a deposition apparatus for
depositing a thin film coating onto substrates within said deposition
chamber and having a cleaning apparatus for removing film deposited onto
the interior surfaces of said deposition chamber, said processing system
further comprising a transport system for sequentially moving substrates
between said processing chambers, said transport system comprising a
plurality of individual carriages for holding substrates undergoing
processing in said system, the total number of carriages of said transport
system being less than the number of processing chambers such that at
least one processing chamber is always empty;
moving a first substrate into a first of said deposition chambers, while
said second deposition chamber is kept empty;
depositing a thin film coating onto said first substrate in said first
deposition chamber and simultaneously cleaning interior surfaces of said
second deposition chamber;
transporting said first substrate from said first deposition chamber to
said second deposition chamber, such that said first deposition chamber is
empty;
depositing a thin film coating on said first substrate in said second
deposition chamber and simultaneously cleaning interior surfaces of said
first deposition chamber.
2. The method of claim 1 wherein the number of carriages in said transport
system is one less than the total number of processing chambers in said
substrate processing system.
3. The method of claim 1 wherein said substrate processing system comprises
at least one other substrate processing chamber and wherein a second
substrate is maintained within said at least one other processing chamber
while said first substrate is processed in said first and second
deposition chambers.
4. A method of processing substrates comprising:
placing a plurality of substrates on a plurality of substrate transport
carriages adapted to move sequentially through a plurality of substrate
processing chambers, at least two of said substrate processing chambers
having a deposition apparatus for depositing a thin film coating onto said
substrates and a cleaning apparatus for cleaning interior surfaces of said
chambers, the number of substrate transport carriages being less than the
total number of processing chambers;
moving one of said substrates into a first deposition chamber and
simultaneously moving a second substrate into a third processing chamber
while keeping a second deposition chamber empty;
depositing a thin film coating onto said first substrate in said first
deposition chamber while operating the cleaning apparatus in said second
deposition chamber and while processing said second substrate in said
third processing chamber;
transporting said first substrate from said first deposition chamber to
said second deposition chamber while continuing to process said second
substrates in said third processing chamber, such that said first
deposition chamber is empty;
depositing a thin film coating onto said first substrate in said second
deposition chamber while operating the cleaning apparatus in said second
deposition chamber and while continuing to process said second substrate
in said third processing chamber.
5. The method of claim 4 wherein the number of substrate transport
carriages is one less than the number of processing chambers.
Description
FIELD OF THE INVENTION
The present invention is generally related to the manufacture of
information recording disks and, more particularly, to the manufacture of
protective films used to protect the recording layer of information
recording disks.
BACKGROUND OF THE INVENTION
Information recording disks such as magnetic recording disks used, for
example, in "hard disks," compact disks, etc. have a structure where a
recording layer is formed on the surface of a substrate which is made of a
metal or dielectric material. In one process for making a magnetic disk
used in a hard disk, a substrate of aluminum (Al), or other suitable metal
or dielectric material is first coated with a nickel-phosphorus (NiP)
layer. Next, an undercoat metal film of suitable material (such as CoCrTa)
is deposited on a surface of the substrate and then a recording layer made
from a thin magnetic film of suitable material is deposited on the metal
film layer. The recording disk is completed by the depositing of a
protective layer over the recording layer.
The protective layer must be composed of a durable film which has
lubricating properties in order to shield the recording layer from impact
and harsh environments. For example, sputtered carbon films (carbon films
which have been deposited by sputtering) have been commonly used as
protective layers. Chemical vapor deposition (CVD) of carbon has also been
used to provide the protective layer. For ease of description, a
protective layer consisting of carbon shall be referred to herein as a
carbon protective layer.
With the recording density of hard disks continuing to increase, it has
become necessary to provide carbon protective layers having a reduced
thickness as compared to those conventionally used in the past. Greater
recording density means less space between the sectors on the hard disk.
When the space between sectors is reduced, the distance between the
recording head and the magnetic recording layer must also be reduced.
Currently available hard disks have a recording density of 1.6 gigabytes
per square inch. Because the carbon protective layer is deposited on the
magnetic recording layer, the thickness of the carbon protective layer
must be reduced in order to minimize the distance between the recording
head and the magnetic recording layer. Current commercial embodiments use
films of between about 100-150 A. This is expected to be reduced to 50-100
A.
FIG. 13 is a schematic plan view of a conventional plasma CVD film
deposition chamber. The deposition chamber 6 is equipped with a pumping
system 61, a process gas delivery system 62 for introducing a process gas
into the film deposition chamber 6, plasma generating means 63 forming a
plasma by providing energy to the process gas which has been introduced by
the process gas delivery system, and a transfer system (not shown) used to
transfer a substrate 9 inside the deposition chamber 6.
The process gas delivery system 62 is designed to introduce an organic
compound gas such as methane (CH.sub.4) into the interior region of the
deposition chamber 6. The plasma generating means 63 is designed to form a
plasma by providing high frequency rf energy to the process gas, and is
comprised of a high frequency power source 633 for supplying high
frequency electrical power by way of a matching box 632 to a high
frequency electrode 631. When plasma of a gas such as methane is formed,
the gas in the plasma decomposes resulting in a thin film of carbon being
deposited on the surface of the substrate 9. The deposited layer of carbon
is then polished to a prescribed thickness.
Carbon films may be broadly divided into amorphous carbon films and
crystallized carbon films. Crystallized carbon films are generally made of
graphite, but some have a lattice structure similar to a diamond and are
referred to as diamond-like carbon (DLC) films. In the manufacture of
carbon films by plasma enhanced CVD using a hydrocarbon compound gas such
as methane, when energy is provided by the collision of negative ions, a
reduction in C--H bonds and C covalent bonds in the plasma occur which
results in more C single bonds thereby resulting in a film having a
diamond lattice structure.
A drawback associated with conventional film deposition apparatuses used to
form carbon protective layers is that during the deposition process the
carbon, used to provide the protective layer on the hard disk, is also
deposited on the exposed surfaces inside the deposition chamber. As the
carbon film buildup increases within the deposition chamber, the film
separates as a result of internal stresses, gravity, etc., resulting in
undesirable carbon particles being released inside the deposition chamber.
These undesirable particles adhere to the surface of the substrates inside
the chamber, forming protrusions on the surface of the protective layer,
resulting in local irregularities in film thickness which can cause head
crashes or signal errors.
FIG. 14 is an exploded, cross-sectional view of the surface of an
information recording disk and a device used to detect defects on the
surface of the disk. When the carbon protective layer is deposited with
the particles adhering on the substrate surface, protrusions 902 are
formed as shown. The particles and the protrusions resulting therefrom can
have a diameter in the range of between about 0.1 to 0.5 microns.
To detect the presence of such protrusions, a glide height test is
performed after the carbon protective layer is deposited on the magnetic
recording layer. The glide height test is a test in which a tip 904 of a
detector 903, as shown in the dashed outline in FIG. 14, is used to scan
the carbon protective layer 901 while being held a predetermined distance
above the surface of the protective layer. In present applications, the
distance d is set at 1 micro-inch. When the tip 904 contacts a protrusion
902 a short circuit is generated within a detection circuit (not shown)
which provides an indication that the hard disk contains a protrusions of
sufficient size to make the hard disk defective.
In conventional film deposition apparatuses, a considerable amount of
carbon particles may be produced by the separation of the carbon film
deposited on the exposed surfaces in the processing chamber which, in
turn, cause many carbon particles to contaminate the surfaces of
substrates. It is difficult to remove all the protrusions and smooth the
substrate in subsequent processing steps. Furthermore, when large
protrusions are deposited by the accumulation of carbon particles,
attempts to remove the protrusions can lead to problems such as scratches
or pitting on the surface of the substrate. Such scratches or pitting
might pass the glide height test, but often are considered defects in
subsequent certifying tests (i.e. recording and playback tests). A
drawback associated with conventional film deposition apparatuses has thus
been the inability to reduce the incidence of product defects.
SUMMARY OF THE INVENTION
The aforementioned and related drawbacks associated with conventional film
deposition apparatuses are substantially reduced or eliminated by the thin
film deposition apparatus of the present invention. The thin film
deposition apparatus of the present invention includes an undercoat
deposition chamber which deposits a layer of chromium to a substrate to be
treated, a magnetic layer deposition chamber which provides a layer of
CoCrTa, or other suitable material, on the previously deposited chromium
layer which acts as a magnetic recording layer, a protective layer
deposition chamber which provides a layer of carbon over the previously
deposited magnetic recording layer to act as a protection layer and a
holding chamber which temporarily holds the resulting information
recording disk upon completion of the processing steps. The protective
layer deposition chamber includes a system which removes excess carbon
particle buildup from within the chamber by selectively introducing heated
plasma and oxygen gas into the interior region of the chamber. The heated
plasma and oxygen interact with excess carbon particles, resulting in the
formation of a gas which is expelled from the interior of the protective
layer deposition chamber by a pumping system. The holding chamber is used
to maintain the newly formed information recording disks while the excess
carbon particles, generated by the protective layer deposition process,
are removed from the interior region of the deposition chamber in order to
prevent the information recording disk from being damaged.
By providing a mechanism to remove excess carbon buildup from the
protective layer deposition chamber, irregularities on the surface of the
information recording disks are eliminated or substantially reduced. The
removal of information recording disk irregularities results in enhanced
signal accuracy and recording disk integrity.
An advantage of the present invention is that it provides a protective film
layer having a planar surface and enhanced protective characteristics.
Another advantage of the present invention is that it effectively prevents
unwanted carbon particle buildup from within the deposition processing
chambers.
Yet another advantage of the present invention is that is increases
information recording disk fabrication yields.
A feature of the present invention is that it uses plasma cleaning to
effectively remove excess carbon buildup from within film deposition
chambers.
Another feature of the present invention is that it provides the ability to
remove treated substrates from respective deposition chambers before
plasma cleaning of the respective chambers begins.
BRIEF DESCRIPTION OF THE DRAWINGS
The aforementioned and related advantages and features of the present
invention will become apparent from the following detailed description of
the invention, taken in conjunction with the following drawings, where
like reference numerals represent like elements, in which:
FIG. 1 is a schematic plan view of the thin film deposition apparatus
according to a first embodiment of the present invention;
FIG. 2 is a schematic cross-sectional side view of the carriage upon which
the substrate manufactured by the film deposition apparatus of the present
invention is placed;
FIG. 3 is a schematic side view of a portion of the structure for moving
the carriage according to the present invention.
FIG. 4 is a schematic side view of a portion of the structure for moving
the carriage according to the present invention;
FIG. 5 is a schematic diagram of the control system for transferring the
thin film deposition apparatus of the present invention;
FIG. 6 is a schematic cross-sectional plan view of a magnetic deposition
chamber of the present invention;
FIG. 7 is a schematic plan view of the protective layer deposition chamber
of the present invention;
FIGS. 8A-8C depict movement of disks through deposition chambers and
holding chambers of the present invention;
FIG. 9 is a time line representing the operations occurring during the
dwell time;
FIG. 10 is a graph illustrating the reduction of carbon particle buildup
when using the protective layer deposition chamber of the present
invention;
FIG. 11 is a schematic plan view of a film deposition apparatus according
to a second embodiment of the present invention;
FIG. 12 is a schematic plan view of a film deposition apparatus according
to a third embodiment of the present invention;
FIG. 13 is a schematic plan view of a conventional plasma CVD film
deposition chamber;
FIG. 14 is an exploded cross-sectional view of the surface of an
information recording disk and a device used to detect defects on the
surface of the disk.
DETAILED DESCRIPTION OF THE INVENTION
The thin film deposition apparatus of the present invention will now be
described with reference to FIGS. 1 through 12. FIG. 1 is a schematic plan
view of a thin film deposition apparatus according to a first embodiment
of the present invention. As shown in FIG. 1, the thin film deposition
apparatus includes a series of substrates 9 contained within a cassette
110. The substrates 9 are mounted inside a loading chamber 1 by the arm
111 of a mounting robot 11. The mounting robot 11 sequentially places the
substrates 9 onto a plurality of carriages 90 which sequentially translate
the substrates through the thin film deposition apparatus. A directional
control mechanism (not shown) is employed to control the direction of
travel of the carriage 90. Directional rotation chambers 3 are used to
rotate the direction of substrate travel ninety degrees (90.degree.). A
more complete description of the directional control mechanism is provided
in Japanese Laid-Open Patent Application 8-274142 which is assigned to the
same assignee as the present invention, and is incorporated fully herein
by reference.
After an individual substrate 9 has been loaded onto the carriage 90 by the
mounting robot 11, the substrate is transferred through gate valve 10 into
a process chamber 4 where the substrate is heated to a prescribed
temperature. In one embodiment, the substrate is heated to a temperature
of about 230.degree. C. After being heated, the substrate 9 is transferred
through another gate valve 10 into a first film deposition chamber 51
where a chromium (Cr) undercoat layer is deposited on the substrate 9.
After the undercoat layer had been deposited, the substrate is transferred
to a first magnetic film deposition chamber 52 where a layer of magnetic
material, such as CoCrTa, is deposited on the undercoat layer to form the
recording layer of the information recording disk. Although described
above as a single processing step, the recording layer can be deposited in
two or more processing steps according to the present invention. As
further illustrated in FIG. 1, in the two layer deposition process, after
the CoCrTa layer is deposited on the undercoat layer in the first magnetic
film deposition chamber 52, the substrate 9 is transferred to a second
undercoat film deposition chamber 53 where a second undercoat layer of Cr
is deposited on the substrate, followed by a second layer of CoCrTa being
deposited on the second undercoat layer of Cr in the second magnetic film
deposition chamber 54. Although the magnetic recording layer has been
described as being CoCrTa, other materials such as CoCrPt and CoCrPtTa may
also be used as magnetic recording layers. After the completion of either
the single layer process or the multi-layer process described above, the
substrate is then transferred to protective film deposition chamber 6
where a protective layer of carbon is deposited on the magnetic recording
layer to complete the fabrication of the information recording disk.
After the final processing steps have been completed, the resulting
information recording disk is then transferred to an unloading chamber 2
where a recovery robot 21 removes the finished information recording disk
from the carriage 90 and places it into a cassette 210 for removal from
the thin film deposition apparatus.
The system used to transfer the substrates through the thin film deposition
apparatus, and the structure and operation of each of the processing
chambers will now be described. FIG. 2 is a schematic cross-sectional side
view of the substrate carriage 90 of the present invention. As shown in
FIG. 2, the substrate carriage 90 is comprised of a substantially
rectangular-shaped member having an upper block portion 906 and a lower
block portion 907. An insulator block portion 905, made from a suitable
material is interposed between the upper block portion and the lower block
portion. The upper block portion 906 includes a pair of plate shaped
members (95a, 95b) each having a generally circular carriage opening (90a,
90b) formed therein. The two carriage openings have a diameter that is
larger than the diameter of the substrate 9. A narrow channel opening is
present on the bottom (208, 209) of carriage openings 90a and 90b,
respectively, for maintaining a holding pawl 91 (hereinafter referred to
as bottom edge holding pawl). Channels are present along the left (210,
214) and right portions (212, 216) of the respective carriage openings for
maintaining side holding pawls 92 therein. The tips of the bottom edge
holding pawls 91 are located on a perpendicular line passing through the
center of the mounted substrate in order to hold the substrate 9 along the
center of its bottom edge.
The side holding pawls 92 on the left (210, 214) and right (212, 216) edges
(hereinafter, side edge holding pawls) of the members (95a, 95b) are
constructed in such a fashion that the side edge holding pawls 92 contact
the side edges of the substrate 9. The movement of the side edge holding
pawls 92 are controlled by plate springs which are opened and closed by
opening/closing rods 93. When a substrate 9 is placed on a carriage 90,
the tip of arm 111 is inserted into the substrate opening to hold the
substrate 9 and situate the substrate relative to the carriage opening 90a
as shown in dashed outline. At this point, the opening/closing rods 93 are
in the open position thereby causing the side edge holding pawls 92 to be
in a position away from the substrate. The arm 111 then moves the
substrate 9 onto the bottom edge holding pawl 91. Next, the
opening/closing rods 93 are placed in the closed position, thereby causing
the side edge holding pawls 92 to contact the sides of the substrate 9 and
maintain the position of the substrate 9 within the carriage opening 90a.
When the substrate 9 is removed from the carriage 90, the operation of the
carriage elements are exactly the reverse of those described above. As the
side edge holding pawls 92 are opened by the movement of the
opening/closing rods 93, the arm 111 for holding the substrate 9 ascend
slightly inside the carriage opening 90a. The arm 111 then moves
horizontally to retract the substrate 9 from the carriage 90. The
substrate 9 is transferred to/from the carriage 90 by being moved
horizontally. As shown in FIG. 2, several small magnets (hereinafter,
referred to as carrier side magnets) 94 are situated along the bottom edge
of the carriage 90 and are arranged by alternating the opposite poles of
the magnets. A magnetic coupling roller 97 is arranged along the bottom of
the carriage 90, with a housing 96 (FIG. 3) interposed between the carrier
side magnets 94 and the coupling roller 97. The magnetic coupling roller
97 is made from rod-shaped members having spirally extending magnets
(hereinafter, referred to as roller side magnets) 971 formed on the outer
circumference thereof. The roller side magnets 971 are comprised of a pair
of magnets (971a, 971b) having opposing polarities. The magnetic coupling
roller 97 is disposed in such a way that the roller side magnets 971a,
971b face the carrier side magnets 94 with the housing 96 being interposed
therebetween. The housing 96 is formed from a highly permeable material
which allows the carrier side magnets 94 and the roller side magnets 971
to be magnetically coupled through the diaphragm 96. Those skilled in the
art will appreciate that other mechanisms for translating the carriage
could also be employed.
The structure of an individual portion of the directional control mechanism
will now be described with reference to FIGS. 3 and 4. FIG. 3 is a
schematic side view of a portion of the mechanism for moving the carriage
90, and FIG. 4 is a schematic side view of a portion of the mechanism for
moving the carriage 90. As shown in FIG. 3, the carriage 90 is placed on a
main roller 951 that rotates about a horizontal axis. Auxiliary rollers
952 rotate about an axis perpendicular to the main roller 951, and are in
contact with the bottom of the carriage 90. Auxiliary rollers 952 press on
either side of the bottom portion of the carriage 90 to prevent the
carriage from rotating.
As shown in greater detail in FIG. 4, housing 96 separates the magnetic
coupling roller 97 and the carrier side magnets 94. Two magnetic coupling
worm gears (97a, 97b) are mounted on rod 972 in the housing 96. A gear 974
is provided on the rod 972. A drive rod 973 having a gear 975, which
engages gear 974, is also present within the housing 96. The drive rod 973
is perpendicular to rod 972, and is connected to a drive motor 98.
Bearings (916, 977) allow rotation of drive rod 973. When the drive motor
98 is actuated, the drive rod 973 rotates causing the gears 974 and 975 to
rotate. This rotation causes magnetic coupling roller 97, to rotate. When
the magnetic coupling roller 97 rotates, the roller side magnets (971a,
971b) rotate. Rotation of the roller side magnets 971 is equivalent to a
plurality of small magnets with alternating magnetic poles in series,
moving in the horizontal direction. As such, the carriage side magnets 94
coupled to the roller side magnets (971a, 971b) move in a linear fashion
along with the rotation of the roller side magnets (971a, 971b), resulting
in the linear movement of the carriage 90.
FIG. 5 is a schematic diagram of the control system for transferring disks
through the thin film deposition apparatus of the present invention.
Individual units of the aforementioned magnetic coupling roller 97,
connecting rod 972, drive rod 973, drive motor 98, and associated parts
are located in each of the chambers 1, 2, 3, 4, 51, 52, 53, 54, 6, 7 and
8. Controller 99 which controls the entire system for translating disks
through the system sends signals to the respective drive motors 98 located
in each of the aforementioned chambers, allowing each drive motor 98 and
the corresponding carriage 90 to be independently controlled.
The specific structure of the processing chambers, used in the thin film
deposition apparatus of the present invention, will now be described.
First, the substrates 9 are heated to a temperature of between about
100-130.degree. C. in preheat chamber 4 (FIG. 1). This causes degassing of
the substrates, i.e., the release of any occluded gas in the substrate.
When a film is deposited without degassing the substrate, gas bubbles may
develop in the film during subsequent deposition, causing the film surface
to become rough as a result of the bubbling. The preheating chamber 4 is
equipped with a gas feeding system (not shown) which introduces an inert
gas, such as nitrogen, into the interior of the preheating chamber, and
heating means for heating the substrate 9 being transferred. Any suitable
heating mechanism, such as an infrared lamp, may be used as the heating
means. It is most practical to control the operation of the heating means
in such a way as to allow the drop in thermal capacity, which occurs when
the preheating chamber 4 is empty, to be corrected. Heating conditions
which avoid changes in the temperature inside the preheating chamber 4
when the preheating chamber is empty should be experimentally determined
beforehand and maintained. For example, in one embodiment, when the
heating means is an infrared lamp, the temperature within the preheating
chamber is constant when the heating means is operated at about 80% power.
When new carriages are transferred into the preheating chamber, the
heating means may then be returned to full power.
Undercoat layer deposition chambers 51 and 53 and magnetic layer deposition
chambers 52 and 54 will now be described. Undercoat layer deposition
chambers 51 and 53 and the magnetic layer deposition chambers 52 and 54,
respectively, deposit undercoat layers or magnetic layers by performing a
sputtering process. The structure of the undercoat layer and magnetic
layer depositing chambers are very similar, the primary difference being
the target materials. Thus, for ease of description, a magnetic layer
deposition chamber will be described and shall apply equally to the
undercoat layer deposition chamber. FIG. 6 is a schematic cross-sectional
plan view of the magnetic layer deposition chamber 52. Magnetic layer
deposition chamber 52 comprises a pumping system 55 to evacuate the
interior of the chamber, a gas delivery system 56 for introducing plasma
gas into the interior of the chamber, a sputter target 57 which is exposed
to the plasma formed in the interior of the chamber, a sputtering power
supply 58 for applying a discharge voltage to the target 57 and a magnet
system 59 located behind target 57. The pumping system 55 is equipped with
one or more vacuum pumps, such as a roughing pump and a cryopump, capable
of reducing the pressure within the interior of the magnetic layer
deposition chamber 52 to about 10.sup.-9 torr. The gas delivery system 56
is designed to allow a prescribed amount of a gas, such as argon, to be
introduced as the plasma gas. The sputtering power supply 58 is designed
to generate a voltage in the range between about -300 to -500 V to be
applied to the target 57 in order to sustain a plasma. The magnet system
59 is used to produce a magnetron discharge and consists of a center
magnet 591, a peripheral magnet 592 in the form of a ring around the
center magnet 591 and a plate-shaped yoke 593, linking the center magnet
591 and the peripheral magnet 592. The target 57 is fixed by means of an
insulating block 571 to the magnetic layer deposition chamber 52. The
magnetic layer deposition chamber 52 is electrically grounded.
After a suitable amount of the plasma gas is introduced by the gas delivery
system 56, the interior of the magnetic layer deposition chamber 52 is
maintained at a prescribed pressure by the pumping system 55, and the
sputtering power supply 58 is actuated. As a result, a plasma is formed
and confined by the magnetic field to a region adjacent to the surface of
target 57. As is well known, this causes sputtering from the target 57,
and the material released from the target 57 is deposited on substrate 9
resulting in the formation of the prescribed magnetic layer on the surface
of the substrate 9. In one embodiment of the present invention, the target
57 consists of CoCrTa, which results in a CoCrTa layer being deposited on
the surface of the substrate 9. As may be seen in FIG. 6, targets 57,
magnet systems 59 and sputtering power supplies 58 are provided on either
side of the substrate in order to form magnetic layers on both sides of
the substrate 9. Also shown in FIG. 6, the targets 57 are somewhat larger
than the substrate 9. In one embodiment, carriage 90 moves inside the
magnetic layer deposition chamber 52 so that two substrates 9 are
sequentially located in front of the targets 57. That is, the forward
substrate 9 is first located in front of the targets 57, where a film is
deposited thereon. The forward substrate is then advanced a prescribed
distance, allowing the rear substrate 9, contained on the carriage 90, to
be positioned in front of the targets 57 so that a magnetic film is
deposited on the rear substrate. FIG. 7 is a schematic plan view of the
protective layer deposition chamber 6 of the present invention. The
deposition chamber of FIG. 7 employs plasma-enhanced chemical vapor
deposition (CVD) to deposit a carbon film. The protective layer deposition
chamber 6 comprises a pumping system 61 for evacuating the interior of
chamber 6, and a gas delivery system 62 for introducing a processing gas
into the interior of the chamber. A plasma (P) is formed to provide energy
to the processing gas introduced by the gas delivery system. The pumping
system 61 is equipped with a vacuum pumping system, such as a
turbo-molecular pump, to establish and maintain a pressure of about
10.sup.-7 torr within the chamber. The gas delivery system 62 is designed
to introduce a processing gas, such as methane and hydrogen, at a
prescribed flow rate. Alternate processing gases such as C.sub.2 H.sub.4
or C.sub.2 H.sub.6 may also be used.
Plasma is formed within chamber 6 by applying a high frequency rf energy to
the processing gas that has been previously introduced. Specifically, the
plasma is generated by a high frequency electrode 631 located within the
protective film depositing chamber 6, and a high frequency power source
633 for supplying power through a matching network 632 to the high
frequency electrode 631. High frequency electrode 631 has a hollow
interior 650, with a plurality of apertures 651 in the front surface
thereof. Gas delivery system 62 is connected to electrode 631 at node 652
such that the processing gas entering the hollow interior 650 of electrode
631 will be uniformly discharged through the apertures 651 at a prescribed
rate. Electrode 631 is mounted on insulating block 634 to the protective
film deposition chamber 6. The protective film deposition chamber 6 is
electrically grounded. High frequency power source 633 supplies electrical
power at a frequency of about 13.56 MHz, resulting in an output of 500 W
to electrode 631. The resulting high frequency electric field results in a
high frequency plasma discharge being produced in the processing gas. In
the plasma, the decomposition of the methane results in the deposition of
carbon on the surface of the substrate 9, forming a carbon protective film
on the substrate. According to the first embodiment of the present
invention, a bias voltage is applied to the substrate 9 during the
deposition of the carbon film. The bias voltage causes ion collisions with
the substrate by extracting ions from the plasma.
As shown in greater detail in FIG. 7, a negative DC power supply 641 and a
second high frequency power source 642 are provided outside the protective
film deposition chamber 6, and are coupled to deposition chamber 6 by a
switch 643. Wire 644 passes through the wall and into deposition chamber
6. A resilient contact 645 is provided at the tip of the wire 644 and
contact 645 is coupled to the upper block 906 (FIG. 2) of the carriage 90
to provide that the negative DC voltage or high frequency voltage is
applied through the carriage 90 to the substrate 9. When high frequency
voltage is applied, suitable capacitance is provided between the second
high frequency power source 642 and the substrate 9, and high frequency rf
energy is applied by means of the capacitance to the substrate 9. As a
result of the interaction between the rf energy that had been applied to
the plasma, a negative self bias voltage is produced at the substrate 9.
The negative DC voltage or negative self bias voltage extracts positive
ions from the plasma to produce collisions with the substrate 9. As
specific examples of the negative DC power source 641 and the second high
frequency power source 642, an output of about -150 V may be used as the
negative DC power source 641, while an output of about 13.56 MHz 50 W may
be used as the high frequency power source 642.
The operating parameters used in one embodiment of the protective film
deposition chamber 6 are outlined in Table 1 below.
TABLE 1
CH.sub.4 gas 20 cc/min
Hydrogen gas 100 cc/min
Pressure inside protective film 2 Pa
deposition chamber
High frequency power 13.56 MHZ 400 W (x2)
Film depositing speed 10-15 A/sec
Film depositing speed 3.5-5 sec
High frequency electrode 631 is large enough to provide plasma adjacent to
two substrates 9, thereby allowing deposition of a carbon film
simultaneously on the two substrates contained within the carriage 90.
High frequency electrodes 631, and associated structures are provided on
both sides of the two substrates 9, allowing the carbon protective film to
be simultaneously deposited on both sides of the two substrates.
A feature provided by the thin film deposition apparatus of the present
invention is that deposition chamber 6 is adapted to form oxygen plasma.
Gas delivery system 62 of the protective film deposition chamber 6 allows
oxygen (O.sub.2) gas to be selectively introduced into the chamber. The
formation of the oxygen plasma is used to prevent unwanted carbon
formation inside the deposition chamber 6. In the deposition chamber of
the present invention, the carbon film deposited on the exposed surfaces
inside the chamber is removed by the oxygen plasma.
Specifically, when oxygen gas is introduced to form an oxygen plasma, an
abundance of oxygen ions is produced in the plasma. Carbon film deposited
on the exposed surfaces of the protective film deposition chamber contains
hydrogen. That is, the film contains C--C bonds as well as C--H bonds.
When such a carbon film comes into contact with oxygen ions, the C--C
bonds or C--H bonds are broken down as follows:
O.sub.2.fwdarw. 20.sup.+ (or 20.sup.-)
(C--C)+4 O.sup.+ (or 4 O.sup.-).sub..fwdarw. 2 CO.sub.2 (or 2 CO+O.sub.2)
(C--H)+2 O.sup.+ (or 2 O.sup.-).sub..fwdarw. CO+H.sub.2 O
The CO.sub.2, CO, O.sub.2 and H.sub.2 O produced by the reactions are all
gases, and are evacuated from the interior of the deposition chamber 6 by
vacuum pump system 61, thereby allowing the carbon film to be removed from
the interior surfaces deposition chamber 6.
The following are exemplary operating conditions for the removal of
unwanted carbon from the interior surface of the process chamber.
TABLE 2
Oxygen flow rate 150 cc/min
Pressure inside chamber 15 Pa
High frequency power 13.56 MHz 500 W (x2)
Pumping system speed 6,000 L/min
When the oxygen cleaning process is performed under the conditions of Table
2, carbon film is removed at a rate of about 600 A/min.
In accordance with the present invention, substrate 9 is removed from
deposition chamber 6 and transferred to holding chamber 7 during the
oxygen plasma removal process. In the present embodiment, holding chamber
7 is a vacuum chamber with its own vacuum pumping system 61, but with no
processing equipment. Holding chamber 7 is separably maintained at an
atmosphere pressure of about 5.times.10.sup.-1 torr by vacuum pumping
system 61. The substrate 9 is transferred to holding chamber 7 during the
oxygen cleaning process by the control unit 99 of the transferring system.
As described above with respect to FIG. 5, control unit 99 independently
controls each of the drive motors 98, allowing independent control.
Substrates 9 are thereby removed from deposition chamber 6 during the
oxygen cleaning.
The time period from when two processed substrates are unloaded from a
carriage 90 in the unloading chamber 2 until two substrates 9 are unloaded
from a subsequent carriage 90 is considered the dwell time. The dwell time
is determined by the longest time period required to execute the
operations of the various chambers. Generally, the magnetic film
deposition in the magnetic film deposition chambers 52 and 54 take the
longest amount of time, so that the time required for magnetic film
deposition and for transferring the substrates to the next chamber is the
dwell time. In other words, the dwell time is the longest process time
(PT) plus the transfer time (TT). When the time taken in the move to the
next chamber differs depending on the chamber, the one taking the most
time is the TT, and the dwell time is PT+TT. The carriages 90 are delayed
in those chambers where the process or transfer times are shorter than the
PT or TT.
During processing, each carriage 90 simultaneously moves to the next
processing chamber at the end of the dwell time. In other words, the
control unit 99 (FIG. 5) of the transferring system operates in such a way
that all drive motors 98 are actuated by the transmission of simultaneous
drive signals when the PT time has elapsed and the carriages 90 are all
moved simultaneously to the next chamber by the TT time. As previously
described, when a carriage 90 reaches the protective film deposition
chamber 6, a carbon protective film is deposited on the substrate by
plasma CVD. When the deposition of the carbon protective film is
completed, the control unit 99 actuates the drive motor 98 of the
protective film deposition chamber 6 and the drive motor 98 of holding
chamber 7, resulting in the carriage 90 being moved from the protective
film deposition chamber 6 (FIG. 8a) to holding chamber 7 (FIG. 8b). At
this time, the control unit 99 does not actuate any drive motor 98 other
than the drive motors 98 of the protective layer depositing chamber and
the holding chamber, and no carriage 90 other than the carriage 90 moving
between the protective layer deposition chamber and the holding chamber is
actuated. After the carriage is placed in holding chamber 7, the holding
chamber 7 is closed, and the gas delivery system 62 in deposition chamber
6 is switched on. Oxygen gas is thus introduced into deposition chamber 6
allowing oxygen cleaning of the chamber as described above.
Next, the control unit 99 of the transferring system sends drive signals to
all the drive motors 98 causing the carriages 90 to move to subsequent
chambers. As shown in FIG. 8(c), the next carriage 90 is moved into the
protective film deposition chamber 6, and the carriage 90 present within
chamber 7 is moved to chamber 8 before being transferred to the unloading
chamber 21.
As may be seen from the aforementioned description, the oxygen cleaning
process may be carried out after every time a carbon protective film is
deposited in deposition chamber 6. In the preferred embodiment, the oxygen
cleaning process is carried out after each carbon deposition to prevent
the buildup of carbon on the exposed interior surfaces of the deposition
chamber 6. No substrate is present within deposition chamber 6 during the
oxygen cleaning and no substrates are exposed to the oxygen plasma.
According to the first embodiment of the present invention, there is one
holding chamber 7 used in the thin film deposition apparatus. This is
related to the processing capacity of the protective film deposition
chamber 6. In the present embodiment, the time for the carbon deposition
in chamber 6, the time for the carriage 90 to move from chamber 6 to
holding chamber 7 and the time for the oxygen cleaning process are added
together resulting in the aforementioned PT+TT.
FIG. 9 is a time line representing the operations occurring during the
dwell time. FIG. 9a depicts an exemplary dwell time in the magnetic layer
depositing chambers 52 and 54, while FIG. 9b depicts the dwell time in the
deposition chamber 6 and holding chamber 7. In an apparatus having a
processing capacity of 450 substrates per hour, the dwell time is 16
seconds ((60.times.60)/(450/2)=16). As shown in FIG. 9a, the 16 second
dwell time used in the magnetic film deposition chambers 52 and 54 is
based on a total of 16 seconds, where the time for the deposition of a
film (SP1) on the first substrate 9 on a carriage 90 is 5.5 seconds. The
time (tr') for the carriage 90 to move in the chambers 52 and 54 in order
to deposit a film on the second substrate is one second. The time for the
deposition of a film (SP2) on the second substrate is 5.5 seconds, and the
time for simultaneously moving all the carriages 90 (TT) is four seconds.
In the protective film deposition chamber 6 and the holding chamber 7, as
shown in FIG. 9b, the CVD is five seconds, the tr' is four seconds, the
(as) is three seconds and the TT is four seconds, the same as above. Thus,
the processing capacity of the protective film deposition chamber 6 is
doubled in the present embodiment. The oxygen cleaning step can thus be
performed after every carbon film deposition with no drop in productivity.
FIG. 10 is a graph illustrating the reduction of carbon particle buildup
when using the protective layer deposition chamber of the present
invention. In a test performed by the inventors, the thin film deposition
apparatus, as described above, was used to deposit a carbon protective
film on a substrate having a diameter of 3.5'. The number of particles
with a diameter of 1 micron or more remaining on the surface of the
substrate was then determined. The vertical axis of FIG. 10 indicates the
number of particles, while the horizontal axis indicates the number of
days since the protective film deposition chamber was first operated. A
carbon film deposition chamber with a processing capacity of about 10,000
substrates per day was used. As seen in FIG. 10, 100 particles were
produced in a conventional apparatus after one day of operation, and this
number increased rapidly thereafter. When this many particles are
produced, a large number of protrusions such as those shown in FIG. 14,
are deposited on the substrate, resulting in a high probability of glide
height test failures.
In contrast, in the protective layer deposition chamber of the present
invention, the number of particles was limited to a few over four days of
processing. If there were any protrusions caused by this number of
particles, they could be completely removed by a tape burnishing process
before the glide height test is administered, which would result in no
glide height test failures.
In accordance with another embodiment of the present invention, the holding
chamber 7 may be located before the protective film deposition chamber 6.
In such a case, after the completion of the process prior to carbon
deposition, a carriage 90 is moved into holding chamber 7 and the
deposition chamber 6 is empty. Carbon removal is then performed in
deposition chamber 6 and the carriage in holding chamber 7 is then moved
to the deposition chamber 6. The protective film is then deposited in the
second half of the cycle. After processing is completed at each station,
all of the gate valves 10 are open, and all the carriages moved to the
next chamber. Carriage 90 is thus again located in the chamber 7 and the
deposition chamber 6 is empty. The aforementioned operations are then
repeated.
When there are a plurality of protective film deposition chambers, there is
a corresponding increase in the number of holding chambers. Each holding
chamber 7 may be located either before or after each deposition chamber 6.
In another embodiment, holding chamber 7 is separated from deposition
chamber 6. In this embodiment, the protective layer deposition chamber can
be emptied by simultaneously moving only the carriages located in the
chambers between the holding chamber 7 and the deposition chamber 6. When
holding chamber 7 is located next to the protective film deposition
chamber 6, the structure of the control system is made more simple as
there are fewer drive motors that need to be independently driven in order
to empty the protective film deposition chambers.
The thin film deposition apparatus according to a second embodiment of the
present invention will now be described with reference to FIG. 11. FIG. 11
is a schematic plan view of a film deposition apparatus according to a
second embodiment of the present invention. The second embodiment differs
from the first embodiment in that the holding chamber 7 has been replaced
with a second protective film deposition chamber 60. The two protective
film deposition chambers 6, 60 have the same structure as that depicted in
FIG. 7. That is, they are used to deposit protective films by plasma CVD
using a composite gas of methane and hydrogen, and a carbon film deposited
on the exposed surfaces inside the chambers can be removed by oxygen
plasma.
According to the second embodiment of the present invention, when a
carriage 90 is transferred to the first deposition chamber 6, the carriage
90 is removed from the second deposition chamber 60, leaving chamber 60
empty. At this time, a mixed gas of methane and hydrogen is introduced
into the first deposition chamber 6, to deposit a carbon protective film
on the substrate 9. At the same time, oxygen gas is introduced into the
empty second deposition chamber 60 thereby removing any carbon inside
chamber 60. The protective film deposition treatment and the carbon
removal treatment are completed in less than one dwell period. Once the
protective layer deposition and the carbon removal treatment have been
completed, the gate valve 10 between the first deposition chamber 6 and
the second deposition chamber 60 is opened, and the drive motors for
chamber 6 and chamber 60 are actuated to move the substrate in the first
deposition chamber 6 to the second deposition chamber 60. In the next
cycle, all of the gate valves 10 are open and all of the drive motors are
operated to move all the carriages to the subsequent chambers. As a
result, a subsequent carriage 90 is again positioned in the first
deposition chamber 6 and the second deposition chamber 60 is empty. Thus,
carbon is deposited in the first and second deposition chambers 6 and 60,
respectively. There is no time wasted such as through tracking operations
in the holding chambers 7. One unit of dwell time is fully used to execute
film deposition and carbon removal. Accordingly, there is no need to
double the carbon protective film depositing capacity as is required in
the first embodiment, making the second embodiment to the present
invention suitable for situations where it would be difficult to double
the film-making capacity.
For the operation of the apparatus according to the second embodiment of
the present invention, carbon film of half the desired thickness may be
deposited in the first deposition chambers 6, and the remaining half of
the film may be deposited in the second deposition chamber 60. The
carriage 90 moves to chamber 60 before half of one unit of dwell time has
elapsed.
FIG. 12 is a schematic plan view of a thin film deposition apparatus
according to a third embodiment of the present invention. In this
embodiment, there are no carriages 90 present in the directional chambers
3 adjacent to the loading chamber 1 and between the magnetic film
deposition chamber 54 and the protective film deposition chamber 6. In the
embodiment illustrated in FIG. 12, the drive motors 98 (FIG. 3) are not
independently controlled as in the first and second embodiments, but
instead are operated simultaneously at the same dwell time.
In operation, after one unit of dwell time has elapsed, all of the
carriages 90 move to the next processing chamber in the process flow,
resulting in the preheating chamber 4 and the first protective film
deposition chamber 6 being empty. As described above, the carbon removal
process is performed using oxygen plasma in the empty first protective
film deposition chamber 6. While the carbon removal process is being
performed on the first protective film deposition chamber 6, a carriage 90
is conveyed into the second protective film deposition chamber 60, where a
carbon film is deposited onto the previously deposited layer.
After one unit of dwell time has elapsed, the first undercoat film
deposition chamber 51 and the second protective film deposition chamber 60
are empty. Accordingly, the carbon removal process is performed in the
second protective film deposition chamber 60 while a carbon protective
film is being deposited in the first protective film deposition chamber 6.
The protective film deposited in the first and second protective film
deposition chambers are deposited in the same manner and have the same
thickness as provided in the second embodiment of the present invention.
After five units of dwell time have elapsed, one complete process cycle
has been completed.
In the third embodiment of the present invention, the carriages are
simultaneously controlled, not independently controlled; thus, the
structure of the transferring system control unit 99 can be simplified.
The foregoing detailed description of the invention is provided for the
purpose of illustration and description and is not intended to be
exhaustive or to limit the invention to the precise embodiments disclosed.
Many modifications and variations of the disclosed invention are possible
in light of the above teaching. For example, thermal CVD can be used to
deposit the protective layer instead of plasma CVD. Accordingly, the scope
of the present invention is to be defined by the claims appended hereto.
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